I only require the main menu (the top one: account | cart | checkout) on desktop view.
The responsive view brings it down to a drop down 'main menu' and further scaling down gives the classic hamburger view - but I do not need either of these.
The category menu is also responsive and has 'Go to..' which allows access to account | cart |checkout, making the responsive main menu superfluous (except on desktop.)
I have tried deleting code in custom.js / header.tpl based on an answer to a similar question posed in 2016. The code had changed a bit, but it was still fairly obvious which bits related to the menu. However, it didn't remove the menu from mobile view unfortunately, nor seem to affect it in any way.
Any help would be greatly appreciated.